The major symptoms of Parkinson's disease, bradykinesia, postural instability, rigidity, and tremor, result principally from a dopaminergic insufficiency within the striatum. Levo-dopa (Sinemet) pharmacology remains the standard treatment strategy which is often preceded by and/or augmented with monoamine oxidase inhibitors, dopamine receptor agonists and cholinergic antagonists. This multipharmacy approach is extremely effective for many years. However, the benefits of levodopa and adjunctive agents wane after 6-7 years and there is an increase in drug- related disabling side effects. In recent years, the transplantation of dopaminergic neurons has been tested as a novel therapeutic strategy for the treatment of Parkinson's disease. Among the donor tissues employed, experimental and clinical evidence favor fetal dopaminergic neurons as the cell type of choice for neural grafting. However, there are a number of practical considerations make widespread fetal grafting difficult and potentially impractical. Principal among these issues is the availability of sufficient numbers of embryonic donors between the ages of 6-10 weeks gestation. The present proposal will employ embryonic dopaminergic nigral neurons which have been genetically modified by transfection with the temperature sensitive SV40 large T antigen. These cells are immortal at 33degreesC but become permanently amitotic when shifted to 37degreesC-39degreesC regardless of any subsequent temperature change. This provides for a virtually limitless supply of clonal dopaminergic neurons which can then easily be rendered amitotic prior to transplantation. We have recently demonstrated that these cells survive grafting, express dopaminergic markers, and reverse functional deficits following transplantation for up to one month in unilaterally nigrostriatal lesioned rats. Furthermore, these cells survive grafting and express dopaminergic markers for up to one month in hemiparkinsonian monkeys. This proposal aims to determine the long-term structural and functional consequence of grafting SV40 transfected dopaminergic cells in rodent and nonhuman primate models of Parkinson's disease. Furthermore, attempts will be made to augment the viability and functional improvement mediated by these implants by cografting these cells with astrocytes or fibroblasts which have been genetically modified to synthesize brain derived neurotrophic factor (BDNF), a neurotrophin which enhances viability of fetal nigral neurons in culture. Lastly, we will determine the ability of a human SV40 transfected dopaminergic cells to survive grafting and mediate functional recovery in unilateral nigrostriatal lesioned rats. These data will determine whether genetically modified neurons can survive grafting long-term and reverse functional deficits in rodent and nonhuman primate models of Parkinson's disease and serve as the foundation for evaluating the potential for this unique source of donor neurons to be employed in future clinical transplantation studies.